The invention relates generally to a conveyor belt and system of the type that follows a helical path and in conventional practice is driven by a driving tower or cage, with the belt exiting one axial end of the helical path and being fed to the other axial end. The conveyor is usually known as a xe2x80x9cspiralxe2x80x9d conveyor system. The invention particularly concerns a modular plastic conveyor belt which articulates to accommodate straight and radius travel as applied to a helical conveyor belt, and to such a belt system wherein the belt is self-supporting and eliminates the need for a helical platform to support the stacked helically extending tiers of the belt, and also eliminates the driving tower. The invention also concerns side guards or side plates which can support successive tiers in such a spiral conveyor belt and which can be used in other helical plastic belts that are not self-supporting.
U.S. Pat. No. 3,938,651 discloses a self-supporting spiral conveyor belt system of a type which has been known, the conveyor belt being formed of metal links or rows which were capable of articulation to travel around the curving path of the helical conveyor belt system, as well as to travel in straight paths from the exit at one axial end of the helical conveyor to be fed back into the other axial end where the belt resumes helical travel. The belt was self-supporting in that it had metal spacers extending up from each side of each belt row, with upper portions of the spacers positioned to bear against the bottom of a link or row above, so that an overlying tier of the belt is supported by the immediately underlying tier. Thus, the metal belt of the referenced patent was arranged in a self-supporting helical stack without need for a support platform or wear strip under each tier and also without the need for a driving tower which normally would engage against inner edges of the belt rows or links to drive the belt up the helical path.
The helical conveyor belt of the xe2x80x2651 patent was not made up of integral modules but rather of rods and various metal components assembled together, with each spacer device being secured to several of the rods to retain it in position.
In the present invention a modular plastic conveyor belt is configured so as to be self-supporting, to be arranged in stacked helical tiers in a spiral conveyor belt system. The modules are integral and formed of injection molded plastic. Each module row may be one integral module or may be several integral modules assembled side by side on a common connecting rod. End members, at least at the edges of each row, preferably are larger as compared to inner ones of the series of interdigited projections of the belt modules, and these end members support plastic frames or side plates which extend upwardly from the end members and which include a generally horizontal bar providing a support surface for a generally similar end member immediately above in a succeeding tier of the belt.
The plastic frames preferably are generally shaped in an inverted xe2x80x9cUxe2x80x9d shape, and in a preferred embodiment the frames extend in an orientation which is somewhat close to parallel to the path of travel, but canted slightly. Alternate rows of modules, in one embodiment, have these frames at alternating positions and canted orientations, in an arrangement whereby the frames can be in overlapped juxtaposed position from module to module, whether at the collapsed inner edge of the helical belt travel or at the expanded outer edge of such a curving path. Further, the preferred belt construction includes a notch and tooth coactive between the top of each frame and the bottom of a belt end member immediately above, for engaging the two tiers together and retaining the belt in stacked relation both as to prevention of side-to-side sliding movement and advancing or retarding movement between tiers.
There are several important advantages of the integral plastic modular conveyor belt of the invention as a stacked tier, self-supporting helical conveyor. One important consideration is that the all-plastic belt eliminates metal contamination which is particularly important in food handling applications, a primary use of helical conveyors. Another advantage is the superior release characteristics of plastics, which improve throughput and reduce product damage and loss. Moreover, the lighter weight of plastic as opposed to a metal belt reduces installation time and helps in the support of the stacked helical tiers by considerably reducing the total weight of the helical stack.
In addition, the lower friction and higher fatigue resistance characteristics of plastic materials can improve belt life in the sometimes stressful travel path of a spiral conveyor. In the case of module rows each formed with a single module, the one-piece integral rows increase stiffness over assembled belts, thus better supporting a load in the absence of a supporting platform.
Still further, the injection molding of the modules allows for very intricate shapes and surface configurations to meet a variety of needs. Also, the modular plastic design allows the support members or frames to be placed at multiple locations across the width of the spiral belt, in order to provide adequate support in wider belt widths. Thus, if each row is made up of several modules, one or more of the interior module ends can include a support frame, to interact with a module end above, providing intermediate support between the edges of the belt.
The modular plastic spiral conveyor system in the self-supporting arrangement is also advantageous over metal in that it can be maintained with hand tools, and in the event of a catastrophic system jam in the spiral conveyor, a higher percentage of the plastic belt is salvageable.
The plastic frames also comprise side guards or side plates that retain products on the belt, and these form an important feature. They are open, allowing air circulation, and can be used effectively on non-self-supporting helical conveyor belts.
It is thus among the objects of the invention to provide for smooth and efficient belt movement in a helical or spiral conveyor belt system, with the belt formed of integral plastic modules with means for self-supporting the belt, with the tiers along the helical path being supported by the tier below. These and other objects, advantages and features of the invention will be apparent from the following description of a preferred embodiment, considered along with the accompanying drawings.